STROPHOMENIDtE. 291 



LepTjENa funiculata. Phillips and Salter. Mem. Geol. Surv., vol. ii, p. 284, 1848. 



— — ^arrawc/e. Sil. Brach.Boheme, p. 92, pi. xxi, figs. 21 — 23,1848. 



— (Strophomena) funiculata, M'Coy. Brit. Pal. Foss., p. 244, 1852. 

 Stkophomena funiculata, Lindstrdm. Gotl. Brach., p. 372, 1860. 



Spec. Char. Semicircular, about twice as wide as long, with the greatest width at the 

 long straight hinge-line ; cardinal extremities prolonged into acute, angular, mucronate 

 wings. Dorsal valve flat or very sHghtly concave to about two thirds of its length, when 

 the valves become suddenly deflected at an obtuse angle to the flattened part; hinge- area 

 linear, fissure arched over by a narrow convex pseudo-deltidium. Ventral valve shghtly 

 convex to about two thirds of its length, when it is suddenly bent upwards so to follow 

 the curves of the opposite valve ; area narrow, fissure arched over with a pseudo- 

 deltidium. External surface covered with coarse, thread-like, radiating radii; a smaller 

 riblet occupying the centre of the interspace left between each pair of ribs ; the whole 

 surface is likewise closely crossed by numerous, fine, concentric lines of growth. In the 

 interior of the dorsal valve the cardinal process is small and bifid, each lobe being grooved 

 along the middle. A small longitudinal ridge divides two elongated, oval depressions 

 left by the adductor muscle. In the interior of the ventral valve are prominent hinge- 

 teeth on each side of the fissure ; the elongated oval muscular depressions are large, and 

 occupy fully half the length of the valve ; they are divided along the middle by a narrow 

 ridge, and are margined by a raised rim. On either side of the posterior portion of the 

 small median ridge are two smaller impressions (heart-shaped), which are due to the 

 adductor or occlusor muscle, while the large impressions on either side of it are referable 

 to the divaricator. The internal surfaces of the valves, close to the muscular impressions, 

 are more or less strongly granulated, and traversed by radiating striae. Two specimens 

 measured — 



Length 8, width 13, depth 1 line. 



Ohs. This is an elegant species, which has many characters in common with 

 Strophomena evglypha, so much so that it has sometimes been mistaken for the young of 

 that species, although it is undoubtedly very distinct and has been so recognised by all 

 palaeontologists. It is, in fact, a much smaller and more transverse species, and the 

 deflected portion of the shell is much smaller in comparison with the flattened part ; the 

 external sculpture differs also in its details; and, as remarked by Prof. M'Coy, "The close, 

 obtuse, sub-uniform striae easily distinguish this species from dwarf examples of St. 

 englypha, and the bilobed boundaries of the muscular impression in the concave or ventral 

 valve are longer and narrower than in St. euglypha!' 



In 1847 I fully illustrated the internal and external characters of the species, and 

 removed it from Orthis to Leptana, a genus in which at that period the larger number of 

 Strophomefiida were classed. 



